MADELYN METTE

Advisor: Ray Rogers
Senior Honors Thesis: 2010

Carbon Isotope Stratigraphy and Magnetic Susceptibility of the Upper Ordovician Daravgai and Gashuunovoo Formations, Gobi-Altai Terrane, Shine Jinst Area, Southern Mongolia

Stable carbon isotopes ratios and magnetic susceptibility were used to explore sea-level shifts and potential climate change in a series of Upper Ordovician marine rocks in southern Mongolia.  Magnetic susceptibility results showed several oscillatory trends that likely represent transgressive and regressive cycles that are not reflected in lithology.  Stable carbon isotope results showed one major positive excursion that likely corresponds to one of the five excursions recognized worldwide during the late Ordovician.  Biostratigraphic constraints are needed to more precisely correlate this section.

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JEFFERY DOBBINS

Advisor: Ray Rogers
Senior Honors Thesis: 2010

A Geochemical Analysis of the Tuffaceous Deposits at Ashfall Fossil Beds, Nebraska

Thirty-seven samples were collected from the volcanic ash bed at Ashfall Fossil Beds State Historical Park in Nebraska for geochemical analysis.  Two hypotheses were tested: (1) the tuff is from a single volcanic eruption, and (2) it is from an 11.93 Ma event from the Yellowstone hotspot.  Major and trace element content was determined using an Energy Dispersive X-ray Spectrometer (EDS) and an X-ray Fluorescence Spectrometer (XRF), respectively.  Results showed one distinct chemical cluster, suggesting a single volcanic source.  Using previously published data, the Ashfall tuff is tentatively correlated to a younger volcanic source, approximately 10.5 Ma.

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NORA CATOLICO

Advisor: Kristi Curry Rogers
Senior Honors Thesis: 2010

Osteohistological Analysis of a Late Cretaceous Herpetofauna (Maevarano Formation, Madagascar)

The complex interplay of factors affecting bone microstructural organization is poorly understood, in spite of the fact that histology serves as a primary data source for the interpretation of fossil vertebrate life histories.  In this thesis, bone histology of appendicular elements from a diverse herpetofauna from the Late Cretaceous Maevarano Formation of Madagascar is analyzed to investigate: 1) the efficiency of osteohistology for identifying particular taxonomic groups; and 2) the osteohistological responses to common environmental stress among different taxonomic groups inhabiting the same stressed, ecosystem. Cluster analyses for histological observations confirms that higher- level taxonomic groups cannot be distinguished on the basis of histological characters, but that optimal numbers of histological clusters may correspond to lower taxonomic groupings.  In addition, the data confirm the hypotheses that functional morphology and environment play significant roles in resultant bone microstructural organization.